Foundations — Virtualization — type 1 and type 2 hypervisors

4.2.40 · D1 · Coding › Operating Systems › Virtualization — type 1 aur type 2 hypervisors

Isse pehle ki aap judge karo kahaan ek hypervisor baithta hai (yahi Virtualization — type 1 and type 2 hypervisors mein poora Type-1-vs-Type-2 ka sawaal hai), aapko kuch words apne karne honge jo parent note quietly assume karta hai. Hum har ek ko zero se banate hain, ek aisi order mein jahan har naya idea sirf pehle se khari chezon par tikta hai.

1. Hardware / "bare metal"

Picture: socho ek flat slab tower ke bottom mein. Is topic mein jo kuch bhi banate hain woh sab is slab ke upar stack hota hai.

Topic ko kyun chahiye: poora Type 1 vs Type 2 ka split yahi ek sawaal hai "kaunsa software is slab ko directly touch karta hai?" Agar aapke dimag mein koi slab nahi hai, toh sawaal bekar hai.

2. Instruction

Picture: chhote cards ki ek conveyor belt; CPU ek card uthata hai, bilkul wahi karta hai jo likha hai, aur agla uthata hai.

Topic ko kyun chahiye: ek hypervisor ka kaam hai conveyor belt ko dekhna aur kuch khatarnak cards ko pakadna pehle hi, isse pehle ki CPU kuch aisa kare jo guest ko karne ki ijazat nahi honi chahiye.

3. Kernel mode vs user mode (CPU privilege rings)

Sare instruction-cards equally khatarnak nahi hote. "2 + 2 add karo" bilkul safe hai. "Saari memory reconfigure karo" ya "disk se seedha baat karo" poori machine crash kar sakta hai. Toh CPU physically khatarnak instructions chalane se mana kar deta hai jab tak woh ek special trusted state mein na ho.

Picture: do rings, ek doosre ke andar. Andar wali ring (kernel) kuch bhi kar sakti hai; bahar wali ring (user) khatarnak controls se door hai. Yahi model CPU Privilege Rings mein hai.

Topic ko kyun chahiye: hypervisor ki trick yeh hai ki woh khud ko sabse andar wali ring mein chalata hai aur har guest OS ko bahar ek kam powerful ring mein dhakelta hai — jabki guest OS ko lagta hai ki woh abhi bhi king hai. Woh demotion hi "trap-and-emulate" ka dil hai.

4. Privileged instruction aur "trap"

Picture: ek tripwire. Guest instructions run karta hua chalta hai; jaise hi woh low-privilege ring mein hote hue kisi privileged instruction par paon rakhta hai, ek wire trip hoti hai aur control hypervisor ke paas aa jaata hai.

Topic ko kyun chahiye: "trap-and-emulate" parent note ka core mechanism hai. Trap = tripwire ka chalna. Emulate = hypervisor ka ek believable result fake karna aur control wapas dena. Trap concept na ho toh samajh nahi aayega ki ek machine safely kaisi bahut saari machines hone ka natak karti hai.

5. Sensitive instruction

Picture: conveyor belt par cards ko colour karo. Grey cards harmless hain. Red cards sensitive hain — woh shared machine state ko touch karte hain.

Topic ko kyun chahiye: Popek & Goldberg rule (parent note) kehta hai ek machine cleanly virtualizable hai sirf tab jab har red (sensitive) card ek tripwire-card (privileged) bhi ho. Agar koi red card tripwire nahi hai, toh woh hypervisor ki nazron se bach jaata hai — aur yahi woh old-x86 POPF problem hai jo parent describe karta hai. Symbols in words:

6. Operating system, host OS, guest OS

Picture: ek Russian nesting doll. Type 2 mein, bahari doll host OS hai; uske andar hypervisor hai; uske andar guest OS hai. Type 1 mein koi bahari host doll nahi hoti — hypervisor khud sabse bahari software hai.

Topic ko kyun chahiye: "host OS present hai ya nahi" literally Type 2 vs Type 1 ka distinction hai. Yeh do words woh vocabulary hain jisme poora comparison table likha jaata hai.

7. Virtual machine (VM)

Picture: ek sealed glass box. Andar, ek guest OS khushi se run karta hai yeh maanta hua ki box ek real computer hai. Hypervisor glass hai — woh guest ko hardware ka ek reflection dikhata hai, kabhi seedhi real cheez nahi. Is bhaari full-machine box ko Containers vs Virtual Machines ke halke approach se compare karo.

Topic ko kyun chahiye: yahi woh product hai jo ek hypervisor banata hai. Upar sab machinery hai; VM output hai.

8. Layer aur "layers to silicon"

Picture: ek relay race. Har extra runner (layer) jise baton lena aur paas karna padta hai woh finish line (hardware) tak pahunchne mein delay add karta hai.

Topic ko kyun chahiye: yahi counting "Type 1 faster hai" ka poora quantitative argument hai, parent note ke Example 3 sameta.

Prerequisite map

Upar se neeche padho: raw hardware se instructions milti hain; kuch instructions ka khatranaakpan privilege modes force karta hai; woh hame traps aur sensitive instructions deta hai, jinका relationship (Popek–Goldberg) safe virtualization ko possible banata hai; layered software phir VMs produce karta hai, aur kitni layers hain woh Type 1 / Type 2 ka jawaab hai.

Equipment checklist

Daayeen taraf cover karo aur khud test karo. Agar koi jawaab surprise kare, toh upar woh section dobara padho.